ManicTime - Track your computer usage and use collected data to accurately tag time.
FreelanceStation - Time tracking and Invoicing for Mac. Built for freelancers.
Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
Qbserve - Freelance time tracking, invoicing, and productivity improvement
RescueTime - Time management software that shows you how you spend your time & provides tools to help you be more productive.
GtimeReport - Export your Google Calendar to Excel and Google Docs Spreadsheets.